The present invention relates generally to devices having internal mixing of diverse fluid components and, more particularly, to fiberglass spraying apparatus.
Fiberglass spraying apparatus or spray guns are known generally and typically serve to mix fluid streams of a resin and a catalyst and apply the resulting fluid mixture to a workpiece. These resin and catalyst fluid streams may be mixed internally or externally with respect to the spray gun housing. If the catalyst and resin fluid streams are mixed externally, the catalyst is typically atomized by and mixed with compressed air internally prior to the catalyst/resin mix. The compressed air serves as a propellant for the atomized catalyst and proides a more uniform mixture of the catalyst and resin fluids. A further discussion of this method of fiberglass spraying may be found in copending U.S. patent application Ser. No. 548,632, filed Nov. 4, 1983, assigned to the same assignees of the present invention.
FIG. 1 shows an exemplary spray gun 10 of this type having a housing 12 with inlet ports 14 and 16 and outlet nozzle 18. Fluid delivery lines 20 and 22 are connected to inlet ports 14 and 16, respectively. Delivery line 20 typically includes inner hose 24 and outer hose 26 arranged coaxially. Fluid catalyst, compressed air, and fluid resin are supplied to housing 12 through inner hose 24, outer hose 26, and delivery line 22, respectively.
Housing 12 includes separate passageways for each of these fluid streams from inlet ports 14 and 16 to outlet nozzle 18. The pasageways for the fluid catalyst and compressed air includes coaxial line 30 having inner line 34, connected to inner hose 24, and outer line 36, connected to outer hose 26. The passageway for the fluid resin is line 32, connected to fluid delivery line 22. Coaxial line 30 and line 32 are connected downstream to valve arrangements 40 and 41, respectively. These valve arrangements control the flow of fluid to output lines 38 and 39, for the catalyst/air mixxture and the fluid resin, respectively. In hand held spray guns, such valve arrangements are typically actuated by mechanical, pneumatic, or hydraulic linkages to manually operable trigger 28. From output lines 38 and 39, the fluid components flow through output nozzle 18 for external mixing and application to the workpiece.
Valve arrangement 40 typically includes needle valve 42 which enters inner line 34 and sets directly on the end of that line or on a valve seat mounted on the end of line 34 to control catalyst flow. Fluid flow from outer line 36 is not directly valved and applies fluid pressure to piston 46. Needle valve 42 is connected to piston 46, and spring 44 biases needle valve 42 to close off catalyst flow against the fluid pressure applied to piston 46. Needle valve 42 is opened when downstream fluid pressure is reduced and the fluid pressure on piston 46 exceeds the biasing force of spring 44. Downstream fluid pressure reduction is caused by actuation of outlet valve 48 which permits fluid flow to outlet line 38. Outlet valve 48 is actuated when trigger 28 is operated. When needle valve 42 is opened, the end of inner line 34 also serves as a nozzle for catalyst flow into the compressed air. Fluid catalyst and compressed air are thus mixed during flow past the valving elements and into outlet line 38.
While such spray gun arrangements perform satisfactorily in some applications, a number of disadvantages and restrictions have become apparent. The use of coaxial lines for the compressed air and fluid catalyst greatly increases both the initial cost and the maintainance and cleaning costs of the spray gun housing and the fluid delivery lines. Also, great care must be taken during use that coaxial delivery line 20 is not twisted, pulled, or bent since inner hose 24 is much more likely to break, stretch, or kink than outer hose 26 or a non-coaxial hose. Further, special fittings, sleeves, and housings are necessary for the coaxial connections between fluid delivery line 20, inlet port 14, and valve arrangement 40.
The versatility of a given spray gun is also restricted. The spray gun described above does not readily permit, for example, use with only a single fluid component supplied through only hose 24 or use with multiple fluid components where the fluid flow through line 36 needs to be controlled directly (as needle valve 42 directly controls flow through path 34). This latter occasion may arise where precise catalyst-air mixture proportions must be maintained or where fluid catalyst and resin are mixed internally.
Previous spray guns of the type shown in FIG. 1 also often do not provide adequate catalyst atomization and even mixing of the catalyst and air, especially when needle valve 42 is just opened. In part this results because needle valve 42 only restricts flow through one of the paths of passageway 30. The configuration of the fluid passageways through valve arrangement 40 also affects the mixing characteristics of the catalyst and air.
Further problems include excessive component wear and difficulty and expense in replacement and cleaning of these components. In particular, needle valves require matching seats to adequately prevent leaks. These needle valves and seats often wear out unevenly or at different rates and yet, since they must be matched, both components are replaced when only one has worn out. Also since the individual components of valve arrangement 40 are in the fluid flow path and exposed to the catalyst/air mixture, the spray gun must be disassembled and/or the individual components cleaned after each use. Otherwise, elements such as needle valve 42 and piston 46 may stick to the passageway walls rather than slide smoothly, thus causing catalyst to back up into other flow lines and preventing proper catalyst atomization.
A similar problem with prior spray guns is with fluid clogging around valve elements and packing seals. Clogging prevents proper valve actuation and increases leakage. Clogging may be caused by trace amounts of oil or water in the compressed air or by catalyst crystals in the fluid catalyst line. In spray gun 10 of FIG. 1, piston 46 has little sliding clearance within the housing bore and these impurities in the fluid flows could, for example, cause temporary or permanent freezing of the piston to the bore walls. Generally, the more complicated the internal valving mechanisms and the smaller the moving component clearances are, the more likely that clogging will occur.
It is therefore an object of the present invention to provide a simplified, inexpensive valve arrangement for use in spray guns.
Another object is the piston of a spray gun apparatus with a reduced tendency to cause clogging and simplified component assembly.
A further object is to provide a fiberglass spray gun with an improved valve arrangement for controlling internal mixing of diverse fluids.
Yet another object is the provison of a fiberglass spray gun having a valve assembly for controlling and improving catalyst atomization and having reduced wear characteristics and an easily cleaned, simplified actuation mechanism.
These and other objects are attained in the provision of a hydraulic valve arrangement for simultaneously opening or closing off the flow of fluid from a plurality of separate and distinct inlet fluid lines to a corresponding plurality of concentric fluid passageways connected to an internal mixing chamber having an outlet nozzle leading therefrom. The valve arrangement includes a spool valve axially slidable within a bore of a housing. This spool valve includes at least a central fluid passageway therethrough and another, concentric fluid passageway defined between the spool valve and the bore. When the spool valve is in the open position, both inlet fluid lines are in fluid communication with the central passageway and the concentric passageway respectively. Fluid flowing through these passageways enters into the interior mixing chamber and exits that chamber through the outlet nozzle. When the spool valve is in the closed position, flow from the inlet fluid lines to the passageways is cut off.
This type of valve arrangement is especially advantageous for use with apparatus feeding multiple fluid component materials through a single valve since the components are mixed at the end of the valve and yet kept separate until that point. For example, in fiberglass spraying apparatus the present invention is employed to mix fluid catalyst and compressed air. Separate inlet fluid lines supply fluid catalyst and compressed air to the central passageway and concentric passageway, respectively. These fluids are thoroughly mixed and the catalyst atomized within the interior mixing chamber prior to exiting through the outlet nozzle. The atomized catalyst is mixed with the resin downstream from that point.
Further objects, advantages, and novel features of the present invention will become more apparent from the following description when considered in conjunction with the accompanying drawings which show, for purposes of illustration only, embodiments in accordance with the present invention.